g.slater and s.synnott   aug 1972   subroutine atm
program to compute standard zenith correction for neutral
atmosphere delay given month day,and site names
ref: jpl iom 391.3-352 25may 1971

p0(i,k) avg. static pressure month i, station k
gam,rh,t0 are temp. gradient,rel. hum. and temp.
k=1 edwards afb
k=2 woomera
k=3 pretoria
k=4 madrid
k=5 wagga

delta's are corrections to station values for each of dsn sites
j=1 ds11
j=2 ds12
j=3 ds13
j=4 ds14
j=5 ds41
j=6 ds51
j=7 ds61
j=8 ds62
j=9 ds42